Actually the object was not so much to keep it from spoiling although that was always a possibility. If you kept Ice to the catch it would stay good for a day or two. The problems were the bears and the martens. Bears would come and tear everything up and the martens were cute as foxes! A tree limb had to be selected that was both strong enough to support the catch, and too flimsy for the animals to climb out on...I'm not sure how effective this method was over time...but the instance I'm thinking of worked well enough to get a nice speckle trout home to the kitchen frying pan...big enough too feed the family!